Everyone is forgetting the situation when Pierre Trudeau decided his legacy would be to bring home the British North America Act and create a made-in-Canada constitution. Pierre was well known for his deep respect of his intellect and nobody else’s; when he could not get agreement from the other federal parties or several of the provinces, he decided to do things his way. This provoked a major PR backlash. Among other things, a suggestion (taken seriously in some quarters) that Britain not pass the necessary enabling legislation. But, more relevant, the Governor General serious mused about not signing the bill if it passed.
We’ve had long drawn out threads before on this site about “what if the Queen refused to sign a bill?” Basically, the monarch acting in a elitist, heavy-handed way - or the governor general - would guarantee changes would happen to prevent this. (Australians can probably clarify, but when the Australian GG called an election with the request of the prime minister many moons ago, to solve a partisan deadlock - there was serious discussion of his appropriate role, across the country.)
So in a British system, the GG or monarch refusing to comply with the wishes of the government would indicate a dispute so serious, so socially disruptive that the GG, who is supposed to be discrete and above the political fray, feels that they need to put the brakes on the situation. The Queen in the UK has a more serious role - the PM talks to her frequently; and like the GG in Canada, the ultimate power is to push the reset button by calling an election. A secondary one is to refuse legislation.
I’ve never heard of it even threatened, but I imagine that should the GG refuse to sign legislation and the government decides to remove him or her, the GG can go down fighting by calling an election first. Traditionally, the government in power remains as a caretaker after an election has been called. (Not sure if the GG has the power to alter that).
However, should the GG exercise the nuclear option, the next election would essentially be either (a) a referendum of whether the GG exercised power correctly or (b) whether the issue over which the GG fought was right. So the GG treads carefully and stays above any partisan fights and simply sits as a weapon of last resort. “Nuclear option” is indeed a more apt description of the power.
I’d like to hear from UK participants, but in my mind, I like the UK parliament better than the Canadian one for a simple reason - it’s twice as big. A typical Canadian parliament has 338 seats; so a majority is 170 or more. The cabinet is typically a little over 30 ministers, but used to be up to 40. Add in deputies, committee heads, etc. and you probably have about 70 or 80 members who have nice positions courtesy of the government. That leaves about 100 or so who are “backbenchers”. maybe 50 to 75 of those are newbies and others seeking to move up in the next shuffle or next election, leaving maybe 20 to 50 who realize they will never be blessed by the party (Or pissed off the current bosses in some way).
Do the same math for Britain - 600MPs, 350 or so in a majority government, subtract the 150 with positions or wannabees angling for a position, and you still have 150 to 200 MPs who find themselves relegated to permanent backbencher in the ruling party. This is a much more unruly bunch, making it difficult to keep a lid on things. it’s a lot easier for dissidents to organize a revolt to threaten the party brass; meaning the party brass has a deeper reason to listen, they ignore the party rank and file at their peril. (also, IIRC, the UK party MP’s have the power to remove their leader/PM, whereas typically in Canada that must wait for the annual(?) party convention of all members)
Canada, OTOH, the leader of a majority has a reputation in recent times for being pretty arrogant and heavy-handed. “My way or the highway” - Pierre Trudeau, Brian Mulroney, Stephen Harper, and Jean Chretien all were fairly dictatorial. The only real risk for any party is the next election or a backbench revolt.
Backbenchers, of course, have the same concern as anywhere - the next election. Some ridings are as they say “yellow dog ridings” - you could run a yellow dog for the right party and the bitch would get elected. The majority of the swing ridings depend on the popularity of the government, and after too long in power, arrogant leaders tend to lose sight of how their actions play in the boondocks. Unlike the USA, whether a government (executive) survives depends on the number of seats the party wins, and the voters know this. Voting for a different member of parliament can change the Prime Minister, whereas voting for a different party in Congress won’t change who is president.